甲乙丙丁张三李四

This internet name combines two common Chinese expressions. '甲乙丙丁' (Jiā yǐ bǐng dīng) refers to the first four Heavenly Stems, which were used in ancient China for timekeeping and can also symbolize a list of items or people. '张三李四' (Zhāng sān Lǐ sì) represents unnamed persons in casual contexts. Altogether, it implies the anonymity of regular folks.